The present invention relates to an optical transmitter-receiver module and an electronic device for use in a single-core bidirectional optical transmitter-receiver system capable of performing transmission and reception with a single-core optical fiber. The present invention relates, in particular, to a digital communication system, which is able to perform high-speed transmission, such as IEEE1394 (Institute of Electrical and Electronic Engineers 1394) and USB (Universal Serial Bus) 2.0.
As a first conventional optical module, there is the one as described in the Japanese Utility Model Laid-Open Publication No. SHO 63-14212. In this optical module, as shown in FIG. 40, an optical module casing 1223 for housing a light-receiving element 1201 is constituted by a conductive material, and the optical module casing 1223 is electromagnetically shielded by being enabled to be grounded. In this optical module, when an optical connector having a ferrule 1207 and an engagement member 1227 is coupled to the optical module casing 1223, the ferrule 1207, constructed of a conductive member, that holds an optical fiber receives no external noise, thus preventing the influence on the light-receiving element 1201.
Moreover, as a second conventional optical module, there is the one as described in the Japanese Utility Model Laid-Open Publication No. SHO 63-24510. In this optical module, as shown in FIG. 41, an outer member 1251 of an optical connector 1250 is made of a resin, and the surface of the outer member 1251 has electric conductivity. After being coupled with the optical connector 1250, an outer member 1252 of an optical module 1254 and the outer member 1251 of the optical connector 1250 come to have same electric potential, and therefore, a high sensitivity characteristic is obtained without receiving the influence of external noises.
In the first conventional optical transmitter-receiver module, the optical module casing 1223 constructed of the conductive member is grounded, and shielding is performed by using the whole body of the conductive ferrule 1207 of the optical connector. On the other hand, in the conventional second optical transmitter-receiver module, shielding is performed by making the surface of the outer member 1251 conductive and making the member as well as the connector 1250 have same potential as the outer member 1252 of the optical module 1254. However, in the conventional first and second optical transmitter-receiver modules, the light-receiving element, which is an internal device, is not shielded. Therefore, it is difficult to obtain high anti-electromagnetic noise characteristic.
Moreover, both the conventional first and second optical transmitter-receiver modules are intended for single-core unidirectional optical transmission and reception. However, in the transmitter-receiver module for single-core bidirectional communications, the light-emitting device and the light-receiving device are arranged adjacent to each other. Therefore, the influence of the electromagnetic noises from the light-emitting device on the adjacent light-receiving device becomes extremely large, and it is extremely important to suppress the electromagnetic noises radiated from the light-emitting device. The light-emitting device and the light-receiving device can obtain a high anti-electromagnetic noise characteristic by being independently shielded. However, if shielding is performed by means of the casing or the like as in the conventional first and second optical transmitter-receiver modules, it is difficult to independently shield the light-emitting device and the light-receiving device, and this consequently leads to a problem that an optical transmitter-receiver module with a high signal-to-noise ratio cannot be realized.